"Color of Colorless" is a small study I did today. I put a white cube on a white board to make sure no local color got involved. I set two lights, one cool and one warm. The temperature contrast of the light sources produced all the colors for this painting. This study maybe the simplest way to demonstrate the warm and cool colors. Most people think the colors "belong" to objects, such as a lemon is yellow, a lime is green, and this cube is white. This "object color" understanding does not help a painter. We paint "perceived colors", which is the interaction among the light source colors, the object color reflectance, and environmental color contributions. If we can see the color (we often not), and be able to mix it, we can paint.